The embodiments described herein relate generally to a systems and methods for measuring the displacement of a rotating shaft and, more specifically, to systems and methods for measuring axial displacement of a shaft within a gas turbine engine using an eddy current sensor.
Gas turbine engines (e.g., jet engines) include a rotating shaft that has compressor and/or turbine blades mounted thereon and rotating therewith. Power can be extracted from the turbine engine via an output shaft (also referred to as a torque shaft) that is coupled between the turbine stage and a gearbox or other power extraction mechanism. Such rotating shafts are supported within the turbine engine via thrust bearings and/or other mechanisms to limit the axial movement of the shaft during use. Excessive axial movement of the shaft relative to the remainder of the engine (e.g., the housing) is an abnormal movement and can be indicative of engine failure (e.g., shaft breakage). When the shaft of a turbine engine breaks, the turbine portion can move backwards because of the effect of combustion gases. Additionally, the compressor mass is decoupled from the rotating system so the shaft and turbine can rotate significantly more quickly. The excessive axial movement of the turbine and/or compressor when the shaft breaks can be sufficiently fast to cause a catastrophic failure of the turbine. Hence, detection of axial movement of the shaft relative to the remainder of the engine can be used to detect engine failure and to prevent additional damage to the engine by, for example, activating a shut off of the engine. In addition to detecting a catastrophic engine failure, detection of the axial shaft displacement over time can provide valuable insight into the rate of wear of engine components and/or potential design improvements to the same.
Alleviating challenges associated with measuring axial shaft displacement within gas turbine engines while the shaft is rotating is an area of interest. Known approaches for measuring displacement of components are susceptible to a number of limitations associated with their application in a gas turbine engine. For example, known methods of measuring displacement using optical techniques are not well suited in the environment within a gas turbine engine, which can be filled with oil mist (for lubrication). The tight clearances between the components of a gas turbine engine can also inhibit known measurement techniques from being used by limiting the size and/or consistency of the target area for detection.
Accordingly, a need exists for improved detection techniques for the measurement of axial displacement of shafts in a gas turbine engine.